[en] Full text: Transfer factors (TFs) of the radionuclides are used to evaluate the biological uptake and the distribution of radioactive contaminants from soil to vegetation. They are defined as the ratio of the specific activity (Bq/g) of the radionuclide in a given plant species and its specific activity in the soil. TFs depend on the geochemical properties of the radionuclides and on the soil characteristics. The sharp variations of the environmental temperature and precipitations may alter the soil properties and influence the geochemical fractionation of the radionuclides, thus changing their TFs. This paper presents the changes of the geochemical fractionation of ²⁴¹Am, ⁶⁰Co and ¹³⁷Cs in Fluvisol soil as a result of temperature increase, freezing and water deficiency. The fractionation of ²⁴¹Am and ⁶⁰Co under different conditions was studied using two sequential extraction procedures. The exchangeable ¹³⁷Cs was determined after extraction with 1 M NH₄NO₃. The influence of the environmental temperature and soil drought on the TFs of the radionuclides from the Fluvisol soil to grass was evaluated. The radioactivity of the leachants was measured by gamma-spectrometry. The results showed that the conditioning at higher temperature or soil drought increased the mobility of ²⁴¹Am and ¹³⁷Cs. The temperature raise caused decrease of the mobile and bioavailable forms of ⁶⁰Co. The conditioning at sharp temperature increase led to higher values of the TFs of the studied radionuclides. This effect was highest for ¹³⁷Cs. key words: transfer factors, radionuclides, Fluvisol soil